By Raul Duarte
How might efforts to cool the planet through solar radiation management affect agricultural productivity?
A seminal paper written by CID Faculty Affiliate Wolfram Schlenker and co-authors, leverages volcanic eruptions as natural experiments to estimate the agricultural impacts of solar radiation management (SRM), a proposed climate intervention aimed at cooling the planet. By examining how stratospheric sulfate aerosols from the eruptions of El Chichón (1982, Mexico) and Mount Pinatubo (1991, Philippines) altered solar radiation, the authors isolate the effect of light scattering on crop yields, an often-overlooked component in prior geoengineering studies. Their results indicate that SRM may have unintended negative consequences for global food production.
Key Findings:
- Scattered sunlight reduces crop productivity: Increased stratospheric aerosol optical depth (SAOD) leads to significant yield losses, 9.3% for maize (a C4 crop) and 4.8% for rice, soy, and wheat (C3 crops), at levels comparable to the Pinatubo eruption. These losses occur because total available sunlight is reduced, outweighing any benefit from increased diffuse light.
- Cooling benefits offset by sunlight reduction: When these yield responses are applied to a future SRM scenario (using aerosol injection to offset warming under the Representative Concentration Pathway 4.5), the gains from temperature reduction are nearly offset by losses from reduced sunlight. The net global effect on agricultural yields is statistically indistinguishable from zero.
- Aerosol characteristics influence crop impact: Aerosols from El Chichón were more forward-scattering and resulted in smaller yield reductions than those from Pinatubo. This suggests that adjusting the radiative properties of SRM particles might reduce some agricultural harm. However, the authors note that this result may also reflect differences in data quality across eruptions.
- Implications for SRM modeling and policy: Many previous studies that focused mainly on temperature and precipitation may have overestimated the agricultural benefits of SRM by neglecting the sunlight-mediated effects of aerosols. The study emphasizes the need for careful assessment before promoting SRM as a climate solution.
Impact and Relevance:
This research provides a novel, empirically grounded assessment of the trade-offs associated with solar geoengineering by showing that efforts to reduce global temperatures could inadvertently lower agricultural productivity. Unlike previous studies that relied on simulation models focused on temperature and precipitation, this study draws on real-world data from volcanic eruptions to capture the full biophysical consequences of SRM, revealing risks that traditional climate models often miss.
The findings are directly relevant to ongoing climate policy discussions. As solar geoengineering gains attention as a potential emergency tool to mitigate global warming, the study cautions that its agricultural side effects (particularly its impact on photosynthesis and crop yields) could undermine its appeal as a reliable climate strategy. It urges policymakers to consider these trade-offs carefully when evaluating SRM's role in climate adaptation and food security planning.
More broadly, the study advances the empirical foundations of climate policy by demonstrating how quasi-experimental methods can inform complex, future-oriented decisions. As climate interventions move closer to real-world consideration, this work illustrates the critical need for comprehensive impact assessments that capture both intended and unintended consequences across sectors and geographies.
CID Faculty Affiliate Author
Wolfram Schlenker
Wolfram Schlenker is the Ray A. Goldberg Professor of the Global Food System at Harvard Kennedy School. Schlenker studies the effect of weather and climate on agricultural yields and migration, how climate trends and the US biofuel mandate influences agricultural commodity prices, and how pollution impacts both agricultural yields and human morbidity. He is a Research Associate at the National Bureau of Economic Research. He currently serves on the Board of Reviewing Editors at Science.
Faculty Publications
Curious to dive deeper into the findings? For a comprehensive analysis and detailed insights, read the full research paper.
Photo by Ivan Torres on Unsplash
